Hole closure nockout plug



June 29, 1948. w. vPFTERS HOLE CLOSURE KNOCK-OUT PUG Filed Nov. 30, 1945 ATTORNEY Patented June 29, 1948 HOLE CLOSURE KNI'KOI'IT'PUG` Walter Peters, Linden, N.,L Ji... assighor: to: The Thomas & Betts Go., Elizabeth, N. J., a corporation of New Jersey Application November 30, 1945, SerialiNo'. 631,960*

2 Claims. l*

'Ilhisvinvention relatesvto'fittings for closing or cofvering various size openings and more particularly to closure plugs adapted toV be secured in cond'uit` openings of 'electrical boxes, or to close other openings suchas theopen ends of'pipes or con'duits, etc.,. and is entitled' herein as a hole closureknockout plug.`

Electrical boxes and` the like, used in raceway systemszofielectrical wiring' installations for housandprotecting' th'e' cables ancl` wires thereof, frequentflyrhaveiholes (known asfknockout open- Ines) whichmust be covered and closed, as in the case of unusedzaperturesin the boxes; and' oceasionally'theopenends of pipcsV or conduitsin the raceways alsoV must be closed; Thisinvention is proposed as asolution. of problems, concerning thef sealing and covering of openings; encounteren` in such installations.

There. is in general: use one type of conventional fitting or closure plug whichhas an obtuse angular form; made of ductile sheet metal, and expansible for. closing knockout. openings in electrical boxes and open. ends of -conduits, etc. However, such` closure plugs are objecti'onal in several respects. For example, difiiculty is expriencedin hammeringv or driving the presentday expansible angular plug into place. This faultis due to the resistance. offered by the plug to hammering pressure',.that is, resistance to the fiatteningV out of its ang'ular.l shape in-reducing it dlownz to disk' for-m by' which toexpand the plug and anchorittinto a racewayi hole to close it. And suchresistance to bending or flattening pressure is' of course dueto the mass or amount of material (sheetrmetal)l which must be dcformed by hammering down'` thepresent-d-ay angular plug into its xfiattene'd andanchored position.

Hammering ordriving on closure plugs `mounted in the walls of electrical boxes damages them and mars` t1e1='`misli'` the'reof, and particular causes vibration which. shak-es'. anfl` loosens the lcoxes1 from; theinfoundations as; well: as Aloosening the electrical parts onthe inside thereof; These faultsa have heretofore'imposedi lmitations: in. the rnanuf.'acture of' conventional' closure plugs, and there'is aI tendency to'confinesthem torsmall sizes or totminimumf diameters:` in order to holdi to` a minimum the mass: of materialli to. be deformed or flattened* when. installina' such plugsV to` close openings which. arefi` foumiii unusecl as7 the wiring mechanicl nears thacOmpIetOn ot. an electrical racewaysystemz i This: iimantion'.` seeks: to solve thel problems.: in question: by prodncing: a new; closure-fitting or plug; off the angulan expansibleadrivenf type. 'he

(cr. zza- 2% angular' bend of this new plugl readilyv mayl be hammered: out: fiat and` the .plug forced ainto.` place without damaging the box,v or. shaking it loose its foundationy or. vibrating, the electrical parts housed therein'. According1y,theuse.ofths new.` plug. does.` not.`` damage. the plaster; or mar other parts of a wallorbuilding',onwhich electrical boxanfd conduit systemszare installed,,and savesthe raceway parts.4 fromabuse.

i Furthermore.. this new ai'igular.` type of; easydrireni plug can be made in large'sizeswhichyield under pressure. or tool impacti when driven. flat into locked position even morereadi-ly. than the present-dayfzsmallisize plug. Thus the new plug herein, irrespectiveof itsv size, is adapted to. be installed; with` light or.: minimum.: driving` pressure.- Theinyentiorr, thereforeenables the manufacturentourmslrthe tradezwith large c1osureplug,- irrespect'ma of;sze,- whichare capable of .the same case' and.` convenience in. their.V installationas the new small sizezplugslherein.v

Incidenta1ly\,.this;new. type of. closure plug4 also can` be' fur-m'fshedin thicker form, that is,pmade of' heaxzier.` gage sheet metal-:thannow in.use; if occasion arisesthetefor, and they drive into' place with.` like-and equal; easezor' 'convenience' without damage tothe-preyiously installed'electrical raceway: system parts orV the walls of. th'e building,

Whet'her smallzorz large, the. new heavy-` or thick gas-.a plugsl herein. function i. alike in that they are just as` easily installed: as the; standardgage new plugs heneim` that is,y theyare as readily instal'l'e; as. plugsf mad-ez off -ductile-- sheet metaliv of standard' or" appravcd:r gase thinness.` whichz meet the:req.ureme1=1ts. oi'the electrical trade andzall such' plugs' (theoldztypeszaswell as the new ones hereinfloloaziousl-'yN are prod'uc'ed' of' the minimum gage sheet metal: which; meet the regulations of theztrade; w

In carrying out this invention, itiwill hommeciated that a new and usefulpredeterminedlength slit: and: lip means is provided in: closure plugs off the angular ty-pe for' reduoing the mass ot metal which mustibedetormed-.when driving them*l into. installed positions.. The slit and;` lip means feature, therefore, providesraz uniformly constanhbendifng massfor all szea'ot: the` new plugsl'l'fereinr In other words, the invention provides aconstant` (whicha manufacturenmay engineer: Into his tools' and diesused in production Operations) to eliminate the variable factors otherwise present in the manufactureV and use of small and large. size closureL plugs. in order that.. all sizes thereof may now-be producedpnzapractical.basis and installed with like ease and simplicity. This feature also applies equally well to thick and thin plugs alike, Thus it is seen that dimensional proportions do not interpose limitations in the manufacture and use of the new closure plugs herein.

An additional feature resides in the automatic sealing or shutting of the new slit and lip means above mentioned as a result of driving the plug into place. This is an important provision inasmuch as electrical code and other regulations i require that closure plugs used in raceway systems present a solid, that is, an imperforate surface in order that their hole-closing function not be impaired. i

It is also pointed out that hole closure plugs must be removable since it may become necessary to open prevlously covered holes in connection with additions or other alterations in electrical raceway systems; and the new plugs herein as readily may be knocked out of an opening by a hammer impact of the same minimum force as first required in installing them.

' I-Ia'ving in mindthe foregoing, an object of the inventlon is to produce angular -expansible types ofdriven closure plugs which can be manufactured inv allsizes and thicknesses (a variety of dimensional proportions) for closing small and large raceway holes alike and .which may be readily and Aconveniently installed with a light tap of a hammer or other impact tool in order to largely, if not entirely, overcome the disadvantages heretoforediscussed.

Av further object is to produce closure plugs having simple means such, for example, as the slit and lip'means above mentioned, which controll and render uniformly constant the bending mass of the plugs for all sizes and all thicknesses thereofand which likewise automatically shuts or seals itself to present an imperforate-surface after the plugs are installed in holes to be closed.

This description and the accompanying drawings explain the invention and indicate further purposes thereof, present it in a manner preferred at this time, demonstrate the features thereof in order to disclose the scope and principle of the invention, thus suggesting further examples of construction' which may develop out of the teachings herein or which may occur to others who wish to avail themselves of the benefits of the invention, and also aid in understanding the problems sought to be solved.

-Figs' 1 thru 8 show three structural examples of small size closure plugs embodyng this invention, while in contrast thereto Figs. 9 thru 12 show the plugsmade in large sizes. In all four cases, whether small or large, thick or thin (any "dimension), a driving impact of minimum force is sufiicient to install the closure plugs, one or the other, in final position.

Incidentally, thesmall size new plugs illustratedl are approximately the maximum size of one make of old type plug on the market.

Fig. 1l shows a top View, Fig. 2 a bott'om or underneath view, and Fig. 3 an end View of this new closure plug. i i Fig. 4 shows a cross-section taken on the line L1-ll, while Fig. 5 is a longitudinal section on Vthe line 5--S.

'Figs 6 .and 7 show a closure plug produced of somewhat thicker sheet metal (double thickness) than the,preVi-ouslytillustrated plugs. Fig. 6 also isa longitudinal section which in effect may be considered as developed on the -line 5-6; and Fig. 'lis a section on the line 1-.-'l.

`before it is driven and fiattened disk-like into anchored position; and Fig. 10 shows a section Fig. 8, in effect, 'shows a modified or third form of construction illustrating a double closing or shutting lip, as distinguished from the single lip rst illustrated.

In general, all the views, except Figs. 6 and 7, may be regarded as illustrating plugs made of standard gage Sheet metal, that is, the minimum Vg'agc for approved manufacture and use.

Fig. 9 shows an elevation of the angular plug (produced in large sizes) inserted in a box hole on the line Him-Hi.

Figi. 11 shows the large size closure plug driven fiat or disk-like into final anchored position in the box hole; and Fig. 12 shows a cross section on the line l 2 |`2.

As to Figs. 9 thru 12, it is to be understood that they demonstrate equally well the installation of the small plugs in box holes or other openings.

Reference is now made to the drawings for a description of examples of structural embodiments of the invention by which to demonstrate how the liinitation-s as to dimensional proportions (small, large, thick and thin, in any permutation thereof) are removed. Also, a consideration is given of the features 'believed to be new in connection with rendering constant thev variables which have arisen in attempting to use old type angular expansible closure plugs and. which in the past have limited them to small sizes.

The drawings show a plug or disk-like member 2 formed of ductile material (sheet metal being used for the purposes herein) and in this instance as having rounded ends 3. A slit 4 is made longitudinally (preferably centered) in the member 2. It is important to observe that each end of the slit 4 terminates short of the spaced end edges 3 of the plug 2. Thu-s the slit ll leaves a connecting or joining span 'I at each end of the slit 4 which bridges the fitting into a one-piece member. The two joining spans 7 constitute a ductile bending mass which renders easy and convenient the installation of the closure plug, as further explained.

Thelformation of the slit 4 provides a longitudinally disposed lip 3 which is bent up and outwardly from the top surface of the plug 2. Thus the slit il and its counterpart lip 8 are of the same length and are symmetrically disposed between the two spaced-apart joining span bending masses 1 which are contiguous with each end edge 3. The formation of the lengthwise slit 4 and its lip 8 may leave said slit open more or less (depending somewhat on the setting and adjustment of vthe punch and d-ie used), and this open slit is automatically shut and made imperforate during the hammering operation of installing the plug in a hole, as will be explained. n

The closure plug, in effect, is divlded into two half .portions 2 and 2, by reason of the two halves being formed at an obtuse angular relation with each other, as will be noted from the sectional and the end views of the drawings. The'line of angular bend is made along the axis of the slit G, as well as the edge of the lip 8, and extends centrally through the ductile joining spans '1. Thus the line of bend is contiguous Vwith or in the plane of the 'slit 4, and in'this construction forms a linear or, in this example, a longitudinal apex or crest produced in the fitting and through the joining spans 7, thereby symmetrically'forming a portion of each joining span on each side of the crest or axis of the angular bend of the plug. w Thus the plug is manufaotured with .its

ananasablvi-ilt-in obtuse' angle (Eig; etc) but operatively flattens; out` into an imper-forat'e plane surface when driven into hole-closingv (Fig. 12). position.

Next, it will be noted that theplug carries integrally fonmed: anchorage means in the form of earsfl; a pair thereof being shown. Each-` ear ez is'carried'z by alongitudinal side edge ofA the plug, thusfproviding' an ear on each side of the slit' and lip llinear-apexmeans 4, 8. The two ears 9- may be-formed parallel .to each other or substantiallyf so.- tocoincide with and`l conform= to the' perimeterof a round' hole tov be closed inasmuch astheclosure-plugs herein are designed more generally forclosing circularapertures (as may be antici-` pated by.` noting-Figs. 9 thru` 12, later explained). Itwill be noted that the two spaced end' edges 3=andlthetwospaced ears 19 ('in this example ofA the-\mvention) are concentric, in that the surfacesfoff these fourportions areformed from a.

common center.

Thus in' appearance, the plug has a partially oircul'ar andidisk-like formation due to its arcuatel end edges 31 and arcuate ears 9, all symmetrical andlconcentric with respect to the body area of theplug. In effect, theends 3 and ears 9l are segmentalfin form, theV ears being made onl a small'z'plug 2 and large plug` 2Lare presented'to distinguish. in size. (although made of like gage Sheet metal). and in. aid of explaining the principle oftheinvention inheringA in the slit and lip means-4; 8 as Well as in the constant mass bending ori joining spans 'Land 1. all of which are included.` in the linear and bending apex of the plug.

It will now be seen that the two spaced joining spans 1 of each plug 2 and 2L are the same length and of the same mass. length of the slit-lip means 4, 8 is increased proportionately in the large plug 2L in order to form its joining spans 1 equal in length and mass to that of the small plug 2. Therefore, all sizes of closure plugs, for a given gage sheet metal, have joining spans 1 which are of equal mass and hence possess the same characteristics in respect to operatively yielding to a minimum of flattening pressure applied on the outside angle of the linear apex or crest of the plugs when driving them into installed position in an aperture to be closed.

Figs. 6 and 7. These two views are to be considered together, in that they show closure plugs of the same construction as heretofore discussed, but they are made of very much thicker sheet metal (say double thickness) than the standard or customary gage ordinarily used in the manufacture of the small size plugs 2 as Well as large size plugs 2L for electrical raceway systems. It will be noted in the drawings that double thickness sheet metal forms a thick plug 2T, with ears 9T of like gage, thus providing a double thickness but half-length joining-span bending-masses 1M at each end of a double thickness lip BT because The ears have outer arcuate surfaces In other words, the

Niy

plugs 2l (Figs; 1 thru 5) which are thesames'iae-y or covering area as the-thiok gage plug-TE:

As further demonstrated by Figs-.I 6 and'` 7, if:r the' metalflis inoreased in gage thickness, tomalfe a heavy or thick gage plug 2111,' the slit i'sfproportionat-ely increased in length at- 45B;` Since the plugs 2 and ZT are the same size (oovering;` area), but ZT'is tw'ice the gageiof plug 2; it: follows that the'linear-apex lip-slit means I`; 4*I``` is lengthened to produce two joining masses 1M which are one-half the length, along the linear' apex, of`V the thinner joining massesfl of plug 2; Therefore, predetermining' the-length of the slit 4Z or 4T controls the mass (amount of' metal) in the deformable joining spans 'l and 'IMl accordan'ce With the dimensional proportions (sizeand thickness) of the closure plug. Such provision renders Constant and uniform themass of? the bridging or joining-spans 'll in the thin plugs: 2 and the mass 1M in= the-thick plugs ZT inorder that the same amount of material be present lin.4 both.

Accorclingly, the invention provides for thin. and thick, as well as small and large plugs, allM having uniform or Constant bend'ingmasses 'l H` and TM, etc. In this way, all'closureplugs, spective of dimensional proportions,` alike are' readily yieldable and give under' the same-driving" or ben'ding pressure applied to thecrest, that is,

the linear or the longitudinalfapexes-oftheplugs for ilattening out the obtuse ang-les (Fig. 10) thereof and expanding them into installed (Eig'. 12) position.

Fg. 8.-I'Iere. the same structural formationvis shown as above discussed, and the-samereference numbers in most part are applied, as in-the= first views. However, adouble or twin: lip` for-J mation 8D is shown along the angularcrestof the. closure plug. These double lips 8D: are punched and. disposed outwardly and face each. other at a slight angle tothe outer surfaceof''` the two angular half portionsof the plug; thusf` forming a: slit similar to that heretofore explained, except that such slit iswder as indicated at 4W. The single lip 8 as Well as the double lip 8D overlay the slits 4 and 4W, respectively, vand perform equally Well when installing the plug for closing any opening and function to shut 01' seal the slit in any of its forms.

The plugs 2, 2L and ZT, etc., are produced in various sizes with the ears 9 and ST spaced apart for particular size openings as, for example, an aperture or knockout hole H (Fig. 9, etc.) in box B of an electrical raceway system. In manufacture, the ears are spaced for slight clearance when first inserted in the hole H in order to be easily placed. Such clearance is shown at C (Fgs. 9 and 10) with the result that the plugs 2, etc. have slightly loose fits when first inserted by the Workman. This undersize spacing of the ears, for particular diameters of box holes H, is advisable in order that irregular or rough-hole edges, and sometimes variations in the tolei'ances thereof, may not interfere with the quick insertion of the plugs into the raceway openings H.

When inserted in the box B, the plug ends 3 overlap and cover the cpposite edge portions of the hole I-I, and the ears 9 extend into the hole beyond the inner surface of the box wall. A light tap or blow from a hammer (applied to the crest or apex of the plug at its parallel slit and lip means 4, 8) acts to flatten out the angle of the plug (Figs. 11 and 12). In response to the driving pressure, the ears 9 expand or spread away from each other, the clearance C disappearing,`

and said ears becoming engaged, under the flattening pressure of la hammer or other driving tool, with the edge of the box hole H. In this way, the closure plugs are anchored in position 'and close the opening H.

The operation of fiattening out the angle or the slitted linear apex of the plug aots simultaneously toclose the overlying lip 8 down into the slit 4, and the closely spaced parallel edges of slit 4 and lip 8 come together in linear engagement. Accordingly, theslit is sealed or shut, and the plug assumes the form of a disk-like cover over the opening H. The lip S seals the slit 4 without necessarily being forced all the way thereinto. its top edge (as in Fig. 12) not entirely flush with the outer surface of the plug, the installation is nevertheless satisfactory due to the aligned sealing of the straight edges of the slit and lip 8, and the reduction of the plug down to approved flattened and imperforate form.

In the event that the closure plug must be removed from the covered opening H, a light tap of adriving tool on the underneath or back side of the plug restores its angular form, also the clearance C, and opens up the slit and lip means 4, 8 (Fig. In this way, the plug of any dimensional proportion is easily removed from the box B or other parts of the raceway system and may be used again.

The disolosure herein explains the principle of the invention and presents the best mode contemplated in applying such principle, so as to distinguish the invention from others; and there is particularly pointed out and claimed, the part, improvement or combination, which constitutes the invention or discovery, as understood by a comparison thereof with the prior art.

-This invention is presented to fill the need for a useful hole closure knockout plug. Various modifications in construction, mode of operation, use and method, may and often do occur to others skilled in the art, especially so after acquaintance With an invention. Accordingly, this In other words, if the lip 8 shows an ear formed on each side edge adapted to extend into the opening, the disk-like member also 'having an angular bend extending longitudinally from end to end and forming a linear apex, with ,a slit extending along the linear apex, the extremities of the slit terminating ladjacent the -ends of the disk-like member, a lip extending along the linear apex and overlying the slit;

whereby a driving pressure exerted on the lip simultaneously flattens the angular bend, foroes the lip into the slit, and expands `the ears into gripping engagement with the surface defining the opening.

2. A fitting as described in claim 1, and having features in addition thereto, comprising two lips formed parallel with each other along the linear apex, one lip on each side of the slit, the adjacentv edges of the two lips overlying the slit; whereby a driving pressure exerted on the lips simultaneously flattens the angular bend, forces the lips into the slit, brings the adjacent edges of the lips together to close the slit, and expands the. ears into gripping engagement with the surfacev defining the opening.

WALTER PETERS.

REFERENCES CITED The following references are of record in the' file of this patent:

UNITED STATES PATENTS Number Name Date 1,491,325 Thomas,'Jr. Apr. 22, 1924 1,850,165 Barnett Mar. 22, 1932 1,980,831 Rosenfield Nov. 13, 1934- 2,240,187 Kingdom et al Apr. 29, 1941 2,324,155 Haynes July 13, 1943 2,370,446 Buchanan Feb. 27, 1945 

